There are many different types of viruses. Taking the more common respiratory viruses as an example, preliminary judgment can be made through laboratory tests, pathogenetic tests, and clinical manifestations. 1. Laboratory tests: blood analysis of patients with viral infections will indicate that the white blood cell count is normal or low, and the lymphocyte count is elevated or lowered. Patients with bacterial infections will have an increase in the total number of white blood cells and neutrophilia. 2. Pathogenetic examination: Pathogenetic examination may include viral antibody test, drug sensitivity test and virus isolation. If relevant pathogens are isolated from the patient’s secretions or blood, it is possible to determine whether there is a viral infection or bacterial infection. 3. Clinical manifestations: Most patients with viral infections will have different degrees of fever. There are many types of viruses and different parts of the disease, so the examination methods will also have greater differences. If there is any doubt, it is recommended to consult a professional doctor in time.